Julie Whittington, RD

Healthy tips from a Registered Dietitian

Low-carb diets appears to impair brain function, including memory and reaction time

Considering going low-carb?  Well, you should think twice…or maybe three or four times.  Research published in the journal Appetite earlier this year found dieters to perform less well on cognitive tests after following low-carb diets as compared to other dieters simply following lower calorie diets that were not low-carb.  Slower reaction times and decreased memory performance were some of the effects of a low-carb diet.

Overall, the study supports what dietitians have known for quite some time…your body needs carbohydrate for optimal brain power as well as overall health and wellness.  A meal plan containing less than 130 grams of carbohydrate per day is not recommended (although low-carb plans often promote carbohydrate at levels as low as 20 grams per day!)  You see, the body needs a minimum of 130 grams of carbs per day in order to have the proper brain and body fuel.  And, even that amount is low.  A healthful diet incorporates 45 to 60 percent of its calories from carbs.  So, a basic 2000-calorie diet would include 225 to 300 grams of carbs per day.

So, which carbs should you eat and when should you eat them?  Well, aim for variety and balanced spacing throughout the day.  Remember that fruits contain about 15 grams carbs per serving, non-starchy vegetables have 5 grams, grains and starches (including starchy vegetables) have 15 grams, milk and yogurt have 12 grams, pure proteins have none and pure fats have none.  For more specifics on serving sizes, see below.

As for which types of carbs provide the most health benefits and which ones are poor choices for your waist-line, blood sugar swings and cravings, here is a small list:

Healthful choices (not an all-inclusive list):

Brown/wild rice, whole grain pasta/bread, quinoa, couscous, corn or whole wheat tortillas, oatmeal, barley, buckwheat, plain popcorn, whole grain dry cereal (such as bran flakes or toasted oat cereal), lowfat organic milk/yogurt (choose ones without added sugars), fresh or frozen fruit (only buy canned fruit if it contains no added sugars or artificial ingredients), fresh or frozen starchy and non-starchy vegetables (watch out for sodium and added sugars in canned vegetables) and small amounts (4-8 oz per day) of juice made from natural fruits or vegetables.

Foods to choose in moderation or avoid (talk to a dietitian about how or if you can incorporate these selections):

Soft drinks (such as soda, sweet tea, lemonade, punch, drink mixers and other fruit drinks), white flours (choose whole wheat bread instead of white bread; limit pastries, cookies and cakes), starchy vegetables with added fat (such as mashed potatoes and French fries), candies, syrups, many ice creams, icings and table sugar.

While it is sometimes possible to incorporate the less healthful carbs into a healthful diet (even I, as a dietitian, love my desserts!), the key is usually moderation and a consideration of your health and weight.  For example, someone with diabetes or obesity would need to be more vigilant than someone at a healthy weight who exercises regularly and maintains good heart health.  That said, you will achieve better overall health and more healthy aging if you focus on the healthful choices and limit or avoid the others.


Visual Aids to Portion Control
1 cup = size of a baseball or a woman’s closed fist or an
open handful, ¼ cup = golf ball, 1 oz cheese = 4 dice or size of a thumb, 2 tbsp = ping pong ball, 1 tsp = thumb tip, water bottle cap, 3 oz meat = deck of cards, palm of hand or checkbook

Exchange Groups:

Grain/starch (15 grams carbs, 0-3 grams protein, fat varies, ~80 calories)

1 oz slice of bread
½ of a 150-190 calorie English muffin/hamburger bun
1 oz dry cereal (~1c Cheerios, ½ c Kashi)
½ c pasta, rice or plain oatmeal
1/3 c quinoa
2 – 4” rice cakes
1 – 4” waffle or pancake (waffle counts as 1 fat)
3 cups popcorn, light airpopped
5 Triscuits or 9 Wheat Thins
1 small cookie or muffin (may also count towards fat)
½ cup starchy veggie (potato/corn/peas/beans)

Protein (7 grams protein, fat varies, ~35-100 calories)

1 oz poultry, fish, beef
1 egg or 2 egg whites
½ c cooked beans (also count as 1 starch)
¼-½ c (about 2-3 oz) tofu (1/6–1/5 of a 14-oz block)
¼ c hummus
½ soy or black bean burger
3 Falafel patties (2” across) (also counts towards fat)
1 oz nuts (~1/4 c) (also counts towards fat)
2 tbsp peanut butter (also counts as 3 fats)
¼ c ricotta cheese
1.5 oz natural cheese (cheddar, parmesan)
2 oz processed cheese (American)

Milk (12 grams carbs, 8 grams protein, fat varies, ~90-150 calories)

1 c milk/milk from soy, rice, almond, hemp, goat
1 c (8 oz) yogurt

Fruit (15 grams carbs, 0 grams fat, 0 grams protein, ~60 calories)

½ c diced fruit (i.e. peaches, pears)
1 small piece of fruit (small apple/banana)
1 cup berries or melon
½ c 100% juice
2-4 tbsp dried fruit

Vegetable (5 grams carbs, ~1 gram protein, 0 grams fat, ~25 calories)

½ c cooked or 1 c raw vegetable
½ c canned vegetable

Fat (5 grams fat, 0 grams carbs/protein unless otherwise noted, ~45-50 calories)

1 tsp butter or oil
1 tbsp lower-fat spread (30-50% vegetable oil, trans-fat free)
1 tbsp vinaigrette
2 tsp mayo-style dressing (i.e. buttermilk ranch), 1tbsp RF
1.5 tsp mayonnaise or 1 tbsp light mayo
1.5 – 2 tsp nut butter
6 almonds, cashews or mixed nuts (~1 tbsp)
16 pistachios/3 macadamia nuts/2 Brazil nuts
4 walnut halves or pecans/10 peanuts
1tbsp seeds/pine nuts
1 slice bacon
2 tbsp half & half or 1 tbsp heavy cream
1 tbsp regular cream cheese, 2 tbsp reduced fat
2 tbsp regular sour cream, 3 tbsp reduced fat
8-10 large olives
1/8 avocado (~2 tbsp)
3 Hershey’s kisses or 2 tbsp chocolate chips (also counts as ½ carbohydrate)


One comment on “Low-carb diets appears to impair brain function, including memory and reaction time

  1. wsm190
    August 3, 2009

    I couldn’t agree more. Before I considered leaving carbs altogether a while back, I researched and learned about Ketosis which is basically a state where your body supplements glycogen from carbs by running the rest of your body, including the brain less efficiently. Healthy carbs over low or no carbs all the way.

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